Make the users empty when there is no passowrd file.

scripts/master/try_job_rietveld.py

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import hashlib
 import json
 import time
 import urllib
 import urlparse
 
@@ skipping 47 matching lines @@
     d.addErrback(log.err, 'error in ValidUserPoller')
     return d
 
   def _GetUsers(self, _):
     """Downloads list of valid users.
 
     Returns:
       A frozenset of string containing the email addresses of users allowed to
       send jobs from Rietveld.
     """
-    pwd = open(self._PWD_FILE).readline().strip()
+    try:

[M-A Ruel, 2012/07/19 11:57:28]

I'd prefer a 
if os.path.isfile()

and be sure to log when the file is not loaded.

[Peter Mayo, 2012/07/19 19:12:52]

SGTM ... once running I'm not sure if the preferred behavior should be to
continue with the previous set, or not allow any until the permissions/contents
of the file are fixed.  Similarly for the web service being unavailable.

Did you want a third cook in this kitchen, or are you and Roger happy to
continue improvements from here?

+      pwd = open(self._PWD_FILE).readline().strip()
+    except IOError:
+      return frozenset([])
+
     now_string = str(int(time.time()))
     params = {
       'md5': hashlib.md5(pwd + now_string).hexdigest(),
       'time': now_string
     }
-
     return client.getPage('https://chromium-access.appspot.com/auto/users',
                           agent='buildbot',
                           method='POST',
                           postdata=urllib.urlencode(params))
 
   def _MakeSet(self, data):
     """Converts the input data string into a set of email addresses.
     """
     emails = (email.strip() for email in data.splitlines())
     self._users = frozenset(email for email in emails if email)
@@ skipping 148 matching lines @@
 
     for ex in exceptions:
       log.msg(ex)
 
   # TryJobBase overrides:
   def setServiceParent(self, parent):
     TryJobBase.setServiceParent(self, parent)
     self._poller.setServiceParent(self)
     self._poller.master = self.master
     self._valid_users.setServiceParent(self)